It is known to provide so-called dowels in concrete paths, usually mostly at the location of joints, more particularly so-called load transfer joints, expansion joints or contraction joints. Such dowels are reinforcement bars with a length of approximately 0.5 m, which mostly are provided in the concrete in the longitudinal direction of the path to be formed. Contrary to traditional reinforcement bars, they mostly consist of smooth-surfaced bars used to form a load-transfer joint of expansion or contraction type. Classically, a whole series of such dowels next to each other is provided at mutual interspaces of, for example, 20 to 50 cm. After having provided the dowels in the concrete path and after the concrete possibly already has hardened, over each series of dowels, in the width of the concrete path, up to just above the dowels, a groove is formed, for example, cut, in the concrete, in order to form the expansion joint. With a possible expansion or contraction, the lower part then forms a breaking zone, whereas the dowels still form a connection between both concrete parts, limiting any vertical movement of the concrete, e.g. caused by load applied by the traffic.
According to a known technique, an example of which is known from U.S. Pat. No. 5,405,212, such dowels are provided in the concrete after having formed the concrete path, when the concrete still is wet. To this aim, a series of dowels is dropped in a controlled manner onto the wet concrete surface, after which these dowels subsequently, by means of vibrating forks, are vibrated into the formed concrete path up to a well-defined depth. Usually, this is performed by means of a device situated at the paving machine by which the concrete path is realized, which device, during the insertion of the dowels, temporarily is stopped in respect to the concrete path, whereas the actual paving machine travels on, whereby, after the insertion of the dowels, the respective device is drawn forward.
This known technique has different disadvantages. An important disadvantage consists in that, as the dowels are inserted into the already formed concrete surface, this surface is disturbed, as a result of which an additional finishing operation, mostly by means of a finishing beam also fixed at the paving machine, must be provided for. Even when using such finishing beam, one will note that at the location where the dowels have been inserted, a demixing or so-called segregation of the concrete takes place, resulting in a poor quality of the finally obtained concrete surface.
Another disadvantage of said known technique consists in that such paving machine is relatively long, as a consequence of which it is difficult to turn and difficult to transport, due to the fact that the device must be able to be stopped temporarily for inserting the dowels, whereas the paving machine travels on, and this device, thus, must be movable in the longitudinal direction of the concrete path, over guide elements, as well as due to the fact that an additional finishing beam is required.
Another disadvantage of said known technique consists in that one never knows with certainty whether the dowels are situated on the right place in the concrete, as they may come loose from below the vibrating forks during insertion.
Also, inserting the dowels according to said known technique requires a large power, for commanding and moving the device along the paving machine, as well as for pushing and vibrating the dowels into the concrete.
In order to counteract the demixing of the concrete, it is already known to realize a concrete path in two layers, whereby before providing the second layer, series of dowels are deposited on the first layer. It is, however, obvious that this, due to the fact that a double layer has to be realized, is a complicated technique and/or a technique necessitating the use of rather complicated machines.